Radiation-sensitive diacrylates

ABSTRACT

Novel diacrylates are prepared by reacting a monohydroxylated acrylic monomer with a polyisocyanate. The reaction product may be polymerized by subjecting to ionizing irradiation, actinic light or to free radical catalysts to form a useful coating material. The diacrylates may also be copolymerized with other radiation sensitive materials.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of application Ser. No.171,321, filed Aug. 12, l971 now abandoned.

BACKGROUND OF THE INVENTION

This invention in general deals with novel compounds which are highlyradiation sensitive. The novel diacrylates, when subjected to ionizingirradiation or to actinic light or to free radical catalysts polymerizeto form extremely strong, stain-resistant materials. These curedmaterials show excellent resistance to the most stringent staining testsand are scratch resistant and mar resistant.

The novel monomers produced in accordance with this invention comprisecompounds having the formula: ##EQU1## wherein R is n-octyl, isooctyl,2-ethylhexyl, decyl, dodecyl, tetradecyl, eicosyl and the like or atertiary alkyl group of the formula wherein R₁, R₂ and R₃ are alkylgroups containing 1 to 5 carbon atoms, such as methyl, ethyl, butyl,pentyl and the like. The total carbon atoms in R₁, R₂ and R₃ may be asgreat as 15 and preferably is from 7 to 9. When R₁, R₂ and R₃ are eachmethyl, R is tert-butyl.

Y is a divalent hydrocarbon radical containing from 6 to 16 carbon atomssuch as phenylene, methylphenylene, trimethylhexamethylene, methylenebis(p-phenylene), methylene bis(cyclohexylene) and the like.

X is hydrogen or methyl; hydrogen is preferred.

The subscript m is an integer having a value of 0 or 1; a value of 1 ispreferred.

These monomers may be utilized as coating materials and may be coatedand cured on various substrates in situ.

A preferred subclass results when Y in Formula I is: ##SPC1##

Or ##SPC2## The two unsatisfied bonds of the methylphenylene radical ofFormula (III) may be located in any positions. The preferred locationsare the 2,4-positions, the 2,6-positions and the 2,5-positions.

A further preferred subclass of compounds occurs when, in Formula (I), Ris the tertiary alkyl radical of Formula (II) and Y is either theradical of Formula (III) or the radical of Formula (IV). Especiallypreferred members of this subclass result when the value of m is 1 and Xis hydrogen. These latter monomers fall within the formulae: ##EQU2##

The novel monomers described above may be formed by reacting amonohydroxylated acrylic monomer having the formula: ##EQU3## wherein R,X and m are as described above, with a polyisocyanate having theformula:

    O=C=N--Y--N= C=O

wherein Y is as described above. When Y is phenylene, methylphenylene ora similar radical, the two isocyanato groups may be located in any ofthe vacant positions. For the toluene diisocyanates the 2,4-positions,the 2,6-positions and the 2,5-positions are preferred. Mixtures ofisomers may be employed. One commercially available mixture of toluenediisocyanates comprises about 80 percent 2,4-diisocyanatotoluene andabout 20 percent 2,6-diisocyanatotoluene.

Basically the monohydroxylated acrylic monomer may be formed by reactinga monofunctional epoxide such as a glycidyl ether or glycidyl esterrepresented by the formula: ##EQU4## wherein R and m are as hertoforedefined, with an ethylenically unsaturated carboxylic acid such asacrylic or methacrylic acid in the presence of a catalyst and preferablyan inhibitor. The catalyst may be any organic base material such astertiary amines exemplified by N-methylmorpholine and triethylamine.Standard inhibitors such as methylquinone may be used. The reaction ispreferably carried out at a temperature of from about 50°C. to 140°C.The reaction is carried out until the acid value is equal to or lessthan about 5. The resulting secondary hydroxy alkyl acrylate ormethacrylate is then reacted with a difunctional isocyanate to form thenovel monomers which contain two acrylate or methacrylate bonds and twourethane linkages.

The reaction between the acrylic monomer and the polyfunctionalisocyanate may be carried out at any temperature but is preferably runat from about 60°C. to about 100°C. Catalysts such as dibutyltindilaurate, triethylamine, butylstanoic acid, and the like may be used topromote the reaction. The acrylic monomer and polyisocyanate may bereacted in a weight ratio of from about 0.5:1 to about 1.5:1.

The monomer produced by the above-described process may behomopolymerized, copolymerized or interpolymerized in the presence offree radical catalysts, by actinic light, or by irradiation. The novelmonomer may be copolymerized or interpolymerized with other monomerssuch as acrylic monomers. These acrylic monomers are exemplified by thealkyl acrylates and aklyl methacrylates and preferably di- ortri-acrylates and methacrylates. The monomer of the invention may becombined with polymers and used as mixtures. If the polymers arecurable, the polymers and the monomer comprising the mixture may beco-cured. If the polymers are not further curable, the monomer may becured in admixture with the polymer. Polymers which may be mixed withthe novel monomers of the invention include poly(alkylacrylates) such aspoly(ethylacrylate), poly(2-ethylhexylacrylate) and poly(butylacrylate),unsaturated polyesters such as poly(propylene maleate phthalate) andpolyethylene maleate; saturated polyesters such as poly(ethyleneadipate)and poly(propylene phthalate); vinyl polymers such aspoly(vinylchloride) and vinylchloride-vinylacetate copolymer; cellulosicpolymers such as cellulose acetate butyrate and cellulose acetate.

In all of the uses described above, mixtures of the monomers of theinvention may be employed rather than a single such monomer. Also, thecompounds of this invention may be mixed with other monomers or polymersand then cured either by using peroxide or by subjecting the mixture toactinic light or to ionizing irradiation. Ordinarily, the mixturecontains at least about 5 precent by weight of a compound or a mixtureof compounds of the invention. The preferred embodiments of thisinvention entail the curing of the novel monomers of this invention orof mixtures of the monomers by actinic light or by ionizing irradiation.

As the monomers prepared in this manner are extremelyradiation-sensitive, and since radiation-sensitivity is both difficultto achieve and to predict, a feature of this invention is to polymerizethe monomers herein by subjecting them to ionizing irradiation.

The term "irradiation", as used herein, means high energy radiationand/or the secondary energies resulting from conversion of electrons orother particle energy to X-rays or gamma radiation. While various typesof irradiation are suitable for this purpose, such as X-rays and gammarays, the radiation produced by accelerated high energy electrons hasbeen found to be very conveniently and economically applicable and togive very satisfactory results. However, regardless of the type ofradiation and the type of equipment used for its generation orapplication, the use thereof in the practice of the invention asdescribed herein is contemplated as falling within the scope of thisinvention so long as the ionization radiation is equivalent to at leastabout 100,000 electron volts.

While there is no upper limit to the electron energy that can be soapplied advantageously, the effects desired in the practice of thisinvention can be accomplished without having to go to above about20,000,000 electron volts. Generally, the higher the electron energyused, the greater is the depth of penetration into the massive structureof the materials to be treated. For other types of radiation, such asgamma and X-rays, energy systems equivalent to the above range ofelectron volts are desirable.

It is intended that the term "irradiation" include what has beenreferred to in the prior art as "ionizing radiation", which has beendefined as radiation possessing an energy at least sufficient to produceions or to break chemical bonds and thus includes also radiations suchas "ionizing particle radiation" as well as radiations of the typetermed "ionizing electromagnetic radiation".

The term "ionizing particle radiation" has been used to designate theemission of electrons or highly accelerated nuclear particles such asprotons, neutrons, alpha-particles, deuterons, beta-particles, or theiranalogs, directed in such a way that the particle is projected into themass to be irradiated. Charged particles can be accelerated by the aidof voltage gradients by such devices as accelerators with resonancechambers, Van der Graaff generators, betatrons, synchrotrons,cyclotrons, etc. Neutron radiation can be produced by bombarding aselected light metal such as beryllium with positive particles of highenergy. Particle radiation can also be obtained by the use of an atomicpile, radioactive isotopes or other natural or synthetic radioactivematerials.

"Ionizing electromagnetic irradiation" is produced when a metallictarget, such as tungsten, is bombarded with electrons of suitableenergy. This energy is conferred to the electrons by potentialaccelerators of over 0.1 million electron volts (mev.). In addition toirradiation of this type, commonly called X-ray, an ionizingelectromagnetic irradiation suitable for the practice of this inventioncan be obtained by means of a nuclear reactor (pile) or by the use ofnatural or synthetic radioactive material, for example, Cobalt 60.

Various types of high power electron linear accelerators arecommercially available, for example, the ARCO type travelling waveaccelerator, model Mark I, operating at 3 to 10 million electron volts,such as supplied by High Voltage Engineering Corporation, Burlington,Massachusetts, or other types of accelerators as described in U.S. Pat.No. 2,763,609 and in British Pat. No. 762,953 are satisfactory for thepractice of this invention.

The monomers and mixtures of monomers described herein whether alone orin admixture with one or more other radiation sensitive monomers willpolymerize acceptably using any total dosage between about 0.2 megaradand about 20 megarads. A "rad" is defined as that amount of radiationrequired to supply 100 ergs per gram of material being treated, and a"megarad" is l0⁶ rads. The total dosage is the total amount ofirradiation received by the monomer. It has been found that the monomersof this invention will polymerize to hard, mar-resistant andstain-resistant films at a total dosage of less than 4 megarads. Thepreferable dosage used is from about 0.5 megarad to about 10 megarads.

The monomers and mixtures of monomers of this invention may also bepolymerized and cured by a free-radical mechanism where free-radicalcatalysts are added and the monomers are heated to polymerize. Anyconventional free-radical catalyst may be used, such as organicperoxides, organic hydroperoxides, or esters thereof. Examples arebenzoyl peroxide, tertiary-butyl perbenzoate, tertiary-butylhydroperoxide, cumene hydroperoxide, azobis(isobutyronitrile) and thelike. The catalysts are generally used in amounts of about 0.1 percentto about 5 percent by weight of the monomer or mixture of monomers.

The monomers and catalysts may be heated to cure. Although curingtemperatures will vary from monomer to monomer, generally temperaturesfrom about 75°F. to about 300°F. are used to bring about thefree-radical cure of the monomers.

In many instances, it may be desirable to polymerize without theaddition of external heat in which cases it is customary to add anaccelerator to the system. Suitable accelerators include cobalt salts,such as cobalt octoate or cobalt naphthenate and amine accelerators suchas N,N-dimethylaniline, N-ethyl-N-hydroxyethyl-m-ethylaniline andN-propyl-N-hydroxyethyl-m-methylaniline.

The novel acrylic monomers may also be co-cured with various othercopolymerizable ethylenically unsaturated monomers or with polymericmaterials using the above-described free-radical mechanisms.

The polymers or copolymers formed by the polymerization of the newmonomers of this invention have great utility as coatings for all typesof substrates. They may be used as protective coatings for wood to formpanels for walls, as coatings on plastics to form floor tiles, ascoatings on metals such as aluminum and steel panels and as coatings forother substrates, and they have the advantage of having superiorstain-resistance, scratch-resistance, mar-resistance, weather-resistanceand chemical-resistance (to acids and bases) and the cured coatings havea high degree of crosslinking. These coatings are also relativelyflexible and capable of forming strong bonds with various substrates.

The coatings may be formed by applying the monomer to a substrate by anyconventional coating means, such as roller coatings, curtain coating,brushing, spraying, etc. The coated article may then be cured either byadding peroxide to the coating or by subjecting the coating to actiniclight or to ionizing irradiation. It is noted that many of the monomershave extremely low viscosity, thus insuring easy application if theproduct is to be used as a coating.

The use of ionizing irradiation to polymerize the monomers is preferredas this method makes it possible to polymerize the coatings at extremelyhigh speeds and thus eliminate the time-consuming baking steps, and asthe use of ionizing irradiation requires no heating, the danger of hightemperatures damaging a heat-sensitive substrate is eliminated.

It is also noted that the use of ionizing irradiation requires nosolvents, thus reducing the danger of poisonous and explosive solventvapors and that the coatings formed by the use of ionizing irradiationare more highly crosslinked and are generally stronger coatings than theconventionally cured coatings.

The following examples set forth specific embodiments of the instantinvention, however, the invention is not to be construed as beinglimited to these embodiments for there are, of course, numerous possiblevariations and modifications. All parts and percentages in the examplesas well as throughout the specification are by weight unless otherwiseindicated.

EXAMPLE 1

A monohydroxylated acrylic monomer was prepared by charging a reactorwith 264.5 grams of a mixture of the glycidyl ethers of n-octyl andn-decyl alcohols (Epoxide No. 7) and 0.67 gram of methylquinone and thereactants were heated at 25°C. After adding 0.67 gram of triethylamine,the temperature was raised to 85°C. and held for 20 minutes and 72 gramsof acrylic acid were added over a 1/2 hour period. The reactants wereheld at about 107°C. for 10 hours until the acid number was 3.63. Thehydroxyl value was 192 and the epoxy equivalence was 2,945.51.

A reactor was charged with 150 grams of the above preparedmonohydroxylated acrylic monomer and heated to 60°C. Dibutyltindilaurate in the amount of 0.1 gram was then added. The mixture wasstirred for about 25 minutes. Over a further period of about 28 minutes39.4 grams of a mixture of toluene diisocyanates comprising about 80percent 2,4-diisocyanatotoluene and about 20 percent2,6-diisocyanatotoluene was added at 92° to 95°C. The reactor was thenheld for about 2 hours at 95°C. The resulting monomer had an NCOequivalence of 90,000 and a hydroxyl value of 89.4.

EXAMPLE 2

A reactor was charged with 296 grams of a mixture of the glycidyl estersof dodecyl and tetradecyl alcohols (Epoxide No. 8) and 0.75 gram ofmethylquinone and heated to 35°C. At that time 0.75 gram oftriethylamine was added and the reactants were held at about 86°C. for20 minutes. Over a period of 11/2 hours 72 grams of acrylic acid wereadded at a temperature of about 103°C. and the reactants were held atthat temperature for an additional 17 hours until the acid number was4.5. The resulting monohydroxy acrylic monomer had an OH value of 159,an epoxy equivalency of 11,042 and an acid value of 5.39.

To 150 grams of the above monomer was added 0.1 gram of dibutyltindilaurate and the mixture was heated to 90°C. To the mixture were addedover a 15 minute period 39.4 grams of a mixture of toluene diisocyanatescomprising about 80 percent 2,4-diisocyanatotoluene and about 20 percent2,6-diisocyanatotoluene and the reaction was continued for an additionalperiod of about 2 hours at 95°C. The resulting monomers had a hydroxylvalue of 77.68.

EXAMPLE 3

A reactor was charged with 296 grams of (Epoxide No. 8) and 0.75 gram ofmethylquinone and heated to 35°C. At that time 0.75 gram oftriethylamine was added and held at about 86°C. for 20 minutes. Over aperiod of 11/2 hours 72 grams of acrylic acid were added at atemperature of about 103°C. and the reactants were held at thattemperature for an additional 17 hours until the acid number was 4.5.The resulting monohydroxy acrylic monomer had an OH value of 159, anepoxy equivalency of 11,042 and an acid value of 5.39.

A reactor was charged with 150 grams of the above monomer and 0.1 gramof dibutyltin dilaurate and heated to 86°C. To the mixture, over a 30minute period, were added 51.7 grams of1-isocyanatomethyl-5-isocyanato-1,3,3-trimethylcyclohexane at about95°C. and the reactants were held at that temperature for an additionalperiod of about 21/2 hours. The resulting monomer had a hydroxyl valueof 36.1.

EXAMPLE 4

A reactor was charged with 36 grams of acrylic acid and heated to 100°C.Over a one hour period, 122.5 grams of the glycidyl ester of a tertiarymonocarboxylic acid (Versatic 911 acid) having from 9 to 11 carbon atomsin the carboxylic acid moiety (Cardura "E" ester) were added and thereactants were kept at that temperature unitl the acid value was lessthan 5. The mixture was then cooled to 95°C. and one drop of dibutyltindilaurate was added and 43.5 grams of a mixture of toluene diisocyanatescomprising about 80 percent 2,4-diisocyanatotoluene and about 20 percent2,6-diisocyanatotoluene were added dropwise and the reactants wereheated for an additional period of about 1/2 hour. The resulting producthad an acid value of 78 and may be represented as a mixture of compoundsof the formulae: ##EQU5## where the value of n is 8, 9 or 10. For eachindividual compound the value of n in one tertiary alkyl group may bethe same as or different from the value of n in the other.

EXAMPLE 5

A reactor was charged with 36 grams of acrylic acid and heated to 100°C.Over a one hour period, 122.5 grams of (Cardura "E" ester) were addedand the reactants were kept at that temperature until the acid value wasless than 5.

To 317 grams of the above monomer were added dropwise a mixture of 111grams of 1-isocyanomethyl-5-isocyano-1,3,3-trimethylcyclohexane and onedrop of dibutyltin acetate over a one hour period and the reactants werekept at 95°-100°C. for an additional period of about 2 hours. Theproduct had an NCO equivalence of 20,000 and a Gardner-Holdt viscosityof Z7- 8 and may be represented as a mixture of compounds of theformula: ##EQU6## where the value of n is 8, 9 or 10. For eachindividual compound the value of n in one tertiary alkyl group may bethe same as or different from the value of n in the other.

EXAMPLE 6

A reactor was charged with 393.8 grams of glycidyl stearate and 0.22gram of methylquinone and heated to 80°C. Over a 1/2 hour period 0.22gram of triethylamine was added at 100°C. and 72 grams of acrylic acidwere then added over an 18 minute period and the reactants were kept at105°C. for an additional 3 hours until the acid number was 4.85. At thatpoint 0.07 gram of dibutyltin dilaurate was added at 95°C. and 45.8grams of a mixture of toluene diisocyanates comprising about 80 percent2,4-diisocyanatotoluene and about 20 percent 2,6-diisocyanatotoluenewere added over a 3 hour and 40 minute period at 95°C. The resultingproduct had an NCO equivalency of 2,910 and a hydroxyl value of 13.30.

EXAMPLE 7

To 90 parts of the composition of Example 5 were added 10 parts of butylacrylate and the mixture was coated onto an aluminum panel and subjectedto electron beam bombardment to a total of 2.6 megarads in a nitrogenatmosphere. The coating was stained with ink, mustard, and merthiolateand was found to be resistant to all stains.

EXAMPLE 8

A reactor is charged with 36 grams of acrylic acid and heated to 100°C.Over a one hour period, 122.5 grams of the glycidyl ester of a tertiarycarboxylic acid (Versatic acid) having from 9-11 carbon atoms in thecarboxylic acid moiety (Cardura "E" ester) are added and the reactantskept at that temperature until the acid value was less than 5. Thereactants are then cooled to 95°C. and one drop of dibutyltin dilaurateis added and 43.5 grams of toluene diisocyanate are added dropwise andthe reactants heated to 95°C. for an additional period of about 1/2hour. The resulting product is a mixture of compounds of the formula:##EQU7## where the value of n is 8, 9 or 10. For each individualcompound the value of n in one tertiary alkyl group may be the same ordifferent from the value of n in the other.

According to the provisions of the patent statutes, there is describedabove the invention and what are now considered to be its bestembodiments. However, within the scope of the appended claims, it is tobe understood that the invention can be practiced otherwise than isspecifically described.

I claim:
 1. A compound represented by the general formula: ##EQU8##wherein a. R is selected from the group consisting of n-octyl, isooctyl,2-ethylhexyl, decyl, dodecyl, tetradecyl, eicosyl and tertiary alkyl ofthe formula ##EQU9## wherein R₁, R₂ and R₃ are alkyl groups containing 1to 5 carbon atoms;b. Y is a divalent hydrocarbon radical containing from6 to 16 carbon atoms; c. X is hydrogen or methyl; and d. m is 0 to
 1. 2.The compound of claim 1 wherein Y is ##SPC3##
 3. The compound of claim 1wherein X is hydrogen.
 4. The compound of claim 1 wherein Y is ##SPC4##5. A compound represented by the general formula ##EQU10## wherein a. Yis selected from the group consisting of ##SPC5##and ##SPC6## and
 6. Acompound represented by the formula ##EQU11## wherein a. R isheptadecyl; andb. Y is ##SPC7##or ##SPC8##